1. Field of the Invention
The present invention relates to de-icing aircraft, and in particular to a method and apparatus for preventing the formation of and removal of ice from the wings of aircraft.
2. Description of the Prior Art
Icing occurs both during flight and when the aircraft are on the ground. Icing of aircraft on the ground occurs both in cooler and in warmer weather. In cooler weather, such as in blizzard conditions, atmospheric moisture accumulates and freezes on aircraft wings. Icing occurs in warm weather after aircraft have been in flight and then land. Ambient temperatures at the high altitudes at which aircraft fly are much cooler than temperatures of ambient air close to the ground. During flight, the components of aircraft wings will cool to the high altitude ambient temperatures. Then, after the aircraft lands, the components of aircraft wings still remain at lower temperatures for significant periods of time. Moisture from warm air close to the ground condenses and then freezes on the portions of the aircraft wings which remain at the cooler temperatures.
It should be noted that as used herein, the term icing aircraft refers to the various types of above-referenced icing phenomena. Further, the term de-icing refers to various apparatus and methods for both removing frozen moisture and preventing the accumulation of frozen moisture on aircraft wings. Thus, as used herein, the scope of the term de-icing includes anti-icing, as well as preventing moisture condensation within aircraft components, such as fuel tanks.
Icing on aircraft wings causes several problems. First, accumulation of ice on the wings of aircraft adds additional weight to the aircraft. This increases the amount of lift required for aircraft to fly. Another problem with ice buildup on aircraft wings is that the airfoil shape for the wings is disrupted. This reduces the amount of lift provided by the wings. Further, a condition related to icing results in moisture condensing on interior components of the wings, such as within fuel tanks. This also poses significant problems.
The primary method for de-icing aircraft on the ground is to spray the aircraft with de-icer fluids. Warm de-icer fluids are sprayed on aircraft components to melt frozen moisture. The temperatures of the aircraft wings are raised to warmer temperatures to prevent moisture condensation. However, the use of de-icer fluids is costly, and poses serious environmental concerns relating to pollution.
Several other prior art systems have been suggested for de-icing aircraft on the ground. One is to blow hot air across the cold wings of aircraft. However, this requires expensive blower systems and large capacity heaters to heat the air. Further, fuel for aircraft is easily ignited, and the use of large capacity heat sources close to aircraft creates serious safety concerns. Another prior art system is to use electric heaters to warm aircraft components. However, electric heating systems are not desirable due to the large power capacity required, and the additional weight such equipment will add to aircraft.
Several prior art means are provided for de-icing aircraft in flight, but they do not operate effectively after the aircraft lands. One in flight de-icing means used with jet aircraft is to pass a portion of hot exhaust gases from an engine discharge through interior portions of aircraft wings. Other prior art, in flight, de-icing means incorporate closed loop liquid circulating systems. One such closed loop liquid circulating system removes heat from the hot exhaust gases of a jet engine discharge, and then distributes the heat to cooler portions of aircraft. Another transfers heat from engine lubricants to cooler portions of aircraft. However, closed loop types of liquid circulating systems typically include components such as heat exchangers and piping which add additional weight to the aircraft, and which are subject to fluid leaks.
In flight types of de-icing systems typically require that the aircraft engine be operating at in-flight levels, and, as a result, they do not operate either efficiently or effectively on the ground. Prior art de-icing methods which are effective for use on the ground are rather costly, and pose safety and environmental concerns.